This application claims the priority of German Patent Application number 199 57 157.0, filed in Germany, Nov. 27, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a control system and method for an internal-combustion engine.
A known valve control system of an internal combustion enginexe2x80x94U.S. Pat. No. 5,031,583xe2x80x94comprises a camshaft with cams of a different profile which actuate an inlet valve or an outlet valve. Between the cams and the valves, rocker levers are provided by means of which, using coupling elements, the lift of the respective valve can be influenced. Furthermore, the camshaft is provided with a phase regulator by means of which the valve timing can be changed. It is a disadvantage of this construction that no measures are taken for monitoring the function of the coupling elements.
This analogously applies to switching elementsxe2x80x94European Patent Document EP 0515520 (corresponding U.S. Pat. No. 5,287,830)xe2x80x94constructed as switching cups interacting with valves of a control system, by means of which, in conjunction with different cams of a camshaft, the lift of the valves can be varied.
It is an object of the invention to take measures in a valve control system for internal-combustion engines in order to be able to check the function of switching elements which are used for adjusting the lift of valves causing the charge cycle control.
According to the invention, this object is achieved by providing a control system for an internal-combustion engine of a piston construction, having several cylinders, said control system comprising at least one camshaft operable to actuate valves for charge cycle control in a combustion space of the internal-combustion engine, at least one valve, as a function of at least one parameter of the internal-combustion engine, being constructed to be adjustable with respect to the lift by switching elements interacting with the camshaft, wherein, for checking the functioning of the switching elements, measuring values (Mw) of the camshaft (inlet camshaft 11) are detected and, in the event of defined deviations from respective defined values, are displayed as a function signal (Fs).
Additional features of preferred embodiments of the invention are described herein and in the claims.
Principal advantages achieved by means of the invention are that, during the operation of an internal-combustion engine utilizing the invention, a malfunctioning of a switching element of the control system, which may result in mechanical damage, can be determined as a function signal. This can take place by using corresponding devices for customer service testing or by vehicle-fixed diagnostic devices, such as OBD (=on-board diagnosis). Torsional vibration signals of a camshaft of the control system are suitable as measuring values for this purpose because the torsional vibration course on a camshaft changes significantly at different valve lifts because of different valve forces. This results in the fact that the torsional vibration peaks of the camshaft will reach a uniform level when all switching elements of the control system according to their function. In the event of possible disturbances of one or several switching elements, a changed torsional vibration coursexe2x80x94alternating large and small vibration peaksxe2x80x94occurs on the camshaft which can be detected by way of Hall generators, induction generators, optical generators or the like. For generating the function signal, the parameters of the switching condition of a phase control of a camshaft, of the switching condition of the valve lift switching, of the rotational speed of the camshaft, and of the oil temperature of the lubricating oil of the internal-combustion engine can also be used.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.